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R/A size not enough?

This is a first for me, not very computer literate. Have been out of the business for 8 years due to being disabled. I want to catch up on the technology and to refresh old skills, so please bare with me.

A friend ask me if he had enough return air and it caught me off guard. What do you think?

He has a 4 ton matched system, 20x25 unit opening. His r/a grilles are as follows. 10x36, 10x24. he also has a 20x24 grille blocked off. My question is, is the first two sizes adequate without the 20x24 opening?

Not to hijack the thread but answers to my question may provide the OP with more insight also. On a very similar topic I have a 4-ton unit and am considering increasing the size of upsatirs return grilles. I have an 18x18 down stairs in the entry hall, a 9.5x6 in the living room, and two 9.5x6 grilles upstairs....for a 2800 sq. ft. house in NJ.

I'm looking at increasing the size of the two upstairs to 14x14 each. Is that enough?

Not to hijack the thread but answers to my question may provide the OP with more insight also. On a very similar topic I have a 4-ton unit and am considering increasing the size of upsatirs return grilles. I have an 18x18 down stairs in the entry hall, a 9.5x6 in the living room, and two 9.5x6 grilles upstairs....for a 2800 sq. ft. house in NJ.

I'm looking at increasing the size of the two upstairs to 14x14 each. Is that enough?

You do have one very good point in your post. The upstair is always warmer due to the heat rising, that is why it is important to have return at the highest point. While using the heat, it allows the warm air to be "re-used" and distributed to downstairs where it is needed. While cooling it takes the heat load off of the house.

In most cases in a 2 story home with one system, you have to heat the downstairs and cool the upstairs.

If the same house had 2 systems, if there were some sort of problem with the upstairs heat or the downstairs cool, you may not even realize it.

You may have to read that one again.

The sizing of the returns you gave aren't normal. 9.5 X 6? Make sure it is a return, also the opening isn't as important as the duct size going to it.

If those are your actual sizes, that wouldn't be enough return.

In a perfect world you would have a return in every bedroom upstairs and at least one at the highest point available upstairs. (of course some return would be needed d/s as well)

Thanks Dash. But not a consumer. Been disabled from job for eight years and rusty in the memory banks. {pain meds tend to do that} Just now able to set at computer for 30min. at a time Ran service for 28 years.

The attitude from others doesn't bother me, you find elitism in any area of expertise.

Thanks Dash. But not a consumer. Been disabled from job for eight years and rusty in the memory banks. {pain meds tend to do that} Just now able to set at computer for 30min. at a time Ran service for 28 years.

The attitude from others doesn't bother me, you find elitism in any area of expertise.

The 10x36 and 10x24 are good for 1500 cfm capacity on the r/a...this leaves you 100 cfm short of required for the 4ton...not a huge deal(may be a little loud and minimal increased amps on blower) The real question is the size of the ducts feeding the cans...should be 18" round or equivalent minimum

The 10x36 and 10x24 are good for 1500 cfm capacity on the r/a...this leaves you 100 cfm short of required for the 4ton...not a huge deal(may be a little loud and minimal increased amps on blower) The real question is the size of the ducts feeding the cans...should be 18" round or equivalent minimum

Really not picking on anyone. I do believe we should all learn a thing or 2. If return is too small you'll draw less amps.

Curious how a small return draws less amps...always assumed with more restriction the blower has to work harder to move air...always want to learn...could you explain?

The blower deal more with moving the air once it is inside the blower chamber. Although the air is having a hard time getting to the blower chamber, the volume of air the blower is dealing with is relatively low for its design.

If you increase the r/a the blower is then running fully loaded, and using more power, but it is being more productive what the power consumed. If you do a cfm / kw used evaluation this should be plain to see.

If you wanted the blower to pull the same amperage as before adding the r/a's, simply lower the blower speed. Your cfm / kw ratio will still be better because the air has less restriction getting to the airhandler.

Go out to your car, using a bottle jack lift the drive wheels so they aren't making contact with the surface. Put it in drive and watch it go. Your cars tire rotation / per gallon of gas likely increased off the charts. Your cars engine has a light load on it, fuel usage is very low. Performance is also very low.

Same thing as before.

Don't try any of this at home, unless you are paying me to show you the correct / safe way in person.